Automatic determination method of inspection region for substrate holding state abnormality inspection and substrate processing system

ABSTRACT

With regard to an inspection region for inspecting abnormality of a holding state of the substrate in an image of the substrate holding unit, (1) an upper end surface of the substrate being normally held by the substrate holding unit is confirmed, (2) based on a position of the upper end surface of the substrate that has been confirmed, a position of the inspection region in a vertical direction is determined, and (3) for a candidate of the inspection region of which the position in the vertical direction has been determined, density thereof at a rotation start time of the substrate holding unit is obtained, a horizontal position of the inspection region is determined based on a difference image integrated value, which is an integrated value of a difference absolute value with density of the same region in an initial state of the substrate holding unit.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority of theprior Japanese Patent Application No. 2016-028228, filed on Feb. 17,2016, the entire contents of which are incorporated herein by reference.

BACKGROUND

Technical Field

The present invention relates to a substrate holding inspection methodin which it is inspected whether or not a substrate is properly held bya substrate holding unit in a case where the substrate is fixed and isrotary processed by a semiconductor manufacturing system and the like,and to a substrate processing system that performs substrate processingby using the substrate holding inspection method. More specifically, thepresent invention relates to an automatic determination method of aninspection region of substrate holding state abnormality inspection.

Related Art

In a semiconductor manufacturing system and the like, as a technique forperforming various processing such as cleaning and coating on asemiconductor substrate such as a wafer (hereinafter, simply referred toas the substrate), there is a substrate processing system that performsthe processing by holding the substrate in a substantially horizontalattitude by a substrate holding member and by supplying process liquidwhile rotating the substrate. To enable high-speed rotation of thesubstrate, such substrate processing system has a plurality of substrateholding members on a circumference corresponding to an outer peripheralshape of a substrate W at an appropriate interval as illustrated in FIG.16. The substrate holding members include a fixing holding member 101for holding the substrate in a fixed state, and an opening and closingholding member 102 for opening and closing when attaching and detachingthe substrate W to and from the system.

The fixing holding member 101 includes a fixed shaft 101 a fixed to abase 103, and a fixed piece 101 b fixed to the fixed shaft 101 a, havinga drum shape, and supporting a peripheral portion of the substrate Wwith a recessed portion on a lateral face thereof. The opening andclosing holding member 102 includes a rotation shaft 102 a fixed to thebase 103, and an opening and closing piece 102 b having a drum shapewith a notch portion 102 c formed in a part thereof and beingeccentrically and rotatably fixed to the rotation shaft 102 a.

Then, to attach and detach the substrate W to and from the system, theopening and closing piece 102 b is rotated on the rotation shaft 102 a,the opening and. closing piece 102 b is moved in a direction away fromthe substrate W, and the notch portion 102 c is faced to the substrateW, whereby abutting of the substrate holding members on the peripheralportion of the substrate W is released. On the other hand, to fix thesubstrate W to the system, the opening and closing piece 102 b isrotated on the rotation shaft 102 a, the opening and closing piece 102 bis moved in a direction approaching the substrate W, and the notchportion 102 c is moved to a position not facing the substrate W.Accordingly, all of the substrate holding members abut on the peripheralportion of the substrate W, whereby the substrate W is sandwichedthereby and held in the horizontal attitude.

However, due to a reason that the substrate W rides on a slant face ofthe recessed portion of the opening and closing piece 102 b or the fixedpiece 101 b and the like, holding of the substrate W by the substrateholding members may be incomplete, or the substrate W may be held in atilted state against a rotation axis thereof. Starting the processing ofthe substrate W in such state may cause a problem in that, due torotation thereof, the substrate W may drop off from the substrateholding member and be damaged or the system itself may be damaged. Toavoid such problem, there have been proposed an inspection system and aninspection method with which a position is inspected by imaging at leastan outer peripheral portion of a disk-shaped object to be measuredplaced on a rotary table by a camera, by processing an image signal thathas been imaged, and by comparing image information with standard imageinformation stored in advance in a storage unit (see, for example, JPH10-321705 A).

As such system, there is also a system that inspects a holding state ofthe substrate by detecting a change in density (or brightness, the samefor the “density” hereinafter) in a part of a region of a photographedimage after a rotation start of the substrate W and the substrateholding member. An exemplary photographed image in this case isillustrated in FIG. 17. In FIG. 17, there are defined a rotation startdetermination region 121 for determining the rotation start of thesubstrate W and the substrate holding member with high sensitivity, anda chuck abnormality determination region 122 for determining abnormalityof the holding state of the substrate with high sensitivity.Particularly from a density change in the rotation start determinationregion 121 and the chuck abnormality determination region 122, therotation start of the substrate W and the substrate holding member andabnormality of the holding state of the substrate W are detected.

Here, the above-described rotation start determination region 121 andthe chuck abnormality determination region 122 as well as a thresholdfor determining each of the regions are often set by an engineer who ispresent at a time of delivering the system. The engineer, however, maynot always have detailed knowledge of image processing and cameraadjustment/optical adjustment, whereby it is sometimes difficult toappropriately set the rotation start determination region 121 and thechuck abnormality determination region 122 as well as the threshold fordetermining each of the regions. Furthermore, in a case where a positionof the camera for photographing an image of the substrate W and thesubstrate holding member is changed after the system is started to beused, it is necessary to reset the rotation start determination region121 and the chuck abnormality determination region 122 as well as thethreshold for determining each of the regions, and in such case, a userneeds to take an action each time to perform resetting by himself, torequest for an engineer having expertise to be dispatched, or the like,whereby it has been imposing a heavy workload on the user.

SUMMARY

The present invention has been devised in view of the above-describedsituation, and an objective thereof is to provide a technique capable ofreducing the workload by detecting a density change between imagesbefore and after a rotation start of the substrate and the substrateholding member and by automatically determining an inspection regionparticularly to be focused on within the images in a case whereabnormality of a holding state of the substrate is inspected.

In order to solve the above issue, the present invention is an automaticdetermination method of an inspection region for abnormality inspectionof a substrate holding state in a substrate processing system including:a substrate holding unit configured to rotate a substrate being held ina substantially horizontal attitude; a processing control unitconfigured to add predetermined processing to the substrate in a statewhere the substrate holding unit is rotated; and an abnormalityinspection unit configured to inspect abnormality of a holding state ofthe substrate by the substrate holding unit, the abnormality inspectionunit including: an imaging unit configured to acquire a first image byphotographing the substrate being held by the substrate holding unitfrom a horizontal direction; a cut out unit configured to cut out, fromthe first image, a second image corresponding to the inspection regionpositioned above the substrate being properly held by the substrateholding unit; and a determination unit configured to obtain a featurequantity indicating the holding state of the substrate by the substrateholding unit and to perform abnormality determination of the holdingstate based on the feature quantity on the second image, the automaticdetermination method including: upper end surface confirming in which anupper end surface of the substrate being normally held by the substrateholding unit is confirmed in the first image; vertical positiondetermining in which a position of the inspection region in a verticaldirection is determined based on a position of the upper end surface ofthe substrate in the first image having been confirmed in the upper endsurface confirming; and horizontal position determining in which, for acandidate of the inspection region for which the position in thevertical direction has been determined, density at a rotation start timeof the substrate holding unit is obtained, a difference image integratedvalue being an integrated value of a difference absolute value withdensity of the same region in an initial state of the substrate holdingunit is obtained, and a horizontal position of the inspection region isdetermined based on the difference image integrated value having beenobtained.

That is, in the present invention, an inspection region for inspectingabnormality of a holding state of the substrate is positioned above thesubstrate that is properly held by a substrate holding unit, and theinspection region is determined as follows. Specifically, in an upperend surface confirming step, an upper end surface of the substrate beingnormally held by the substrate holding unit is confirmed within a firstimage. In a vertical position determination step, based on a position ofthe upper end surface of the substrate that has been confirmed, aposition of the inspection region in a vertical direction is determined.Furthermore in a horizontal position determination step, for a candidateof the inspection region of which the position in the vertical directionhas been determined, density thereof at a rotation start time of thesubstrate holding unit is obtained, a difference image integrated value,which is an integrated value of a difference absolute value with densityof the same region in an initial state of the substrate holding unit, isobtained, and a horizontal position of the inspection region isdetermined based on the difference image integrated value that has beenobtained.

Accordingly, it is possible to automatically set the inspection regionby using the upper end surface of the substrate being normally held bythe substrate holding unit as a reference to a position higher by apredetermined gap amount from the upper end surface of the substrate. Asa result, by appropriately setting the gap amount in advance, it ispossible to automatically determine the inspection region with which itis possible to determine abnormality of the holding state of thesubstrate with higher accuracy.

In addition, it is preferred that the inspection region be set to aplace where there is a smallest possible change within the image due toa factor other than a face deflection of the substrate. Thus, for thecandidate of the inspection region of which the position in the verticaldirection has been determined, the density thereof at the rotation starttime of the substrate holding unit is obtained, and the horizontalposition of the inspection region is determined based on the differenceimage integrated value, which is the integrated value of the differenceabsolute value with the density of the same region in the initial stateof the substrate holding unit. Accordingly, it is possible to suppressinconvenience that the inspection region is automatically set to aposition at which the image is largely changed from that in the initialstate due to the factor such as the face deflection of the substrate.

In the present invention, in the horizontal position determining, thehorizontal position of the inspection region may be a position at whichthe difference image integrated value is the minimum.

Accordingly, it is possible to more certainly reduce a possibility thata second image within the inspection region is influenced by a shadowthat moves when the substrate holding unit is rotated and the like. Itis also possible to relatively increase a degree of influence on thesecond image due to the face deflection of the substrate, whereby it ispossible to perform abnormality determination of the holding state ofthe substrate with high sensitivity.

In the present invention, in the upper end surface confirming, theposition of the upper end surface of the substrate may be confirmed to aposition at which a difference value of density between a pixel at apredetermined horizontal position of the first image and an adjacentpixel related to the vertical direction is equal to or greater than apredetermined multiple of a standard deviation of density in each pixelrelated to the vertical direction. Accordingly, it is possible toautomatically confirm the upper end surface of the substrate beingnormally held by the substrate holding unit by using easier algorithm.

In the present invention, the feature quantity may be determined basedon the difference image integrated value, and a threshold of the featurequantity used for the abnormality determination of the holding state ofthe substrate may be determined based on an average value and a standarddeviation of the difference image integrated value in the inspectionregion of the first image during rotation of the substrate holding unit.Accordingly, the threshold that is compared with a feature quantity indetermining whether or not the holding state of the substrate isabnormal may be determined based on statistical data of the differenceimage integrated value of the inspection region within the first imageduring rotation of the substrate holding unit.

In the present invention, the first image at the rotation start time ofthe substrate holding unit may be an image in which the substrate beingheld by the substrate holding unit is photographed from the horizontaldirection by the imaging unit at a point of time when the differenceimage integrated value within a predetermined rotation startdetermination region exceeds a predetermined second threshold.

That is, as a determination reference for determining the rotation starttime of the substrate holding unit from the image, it is focused on thedifference image integrated value of a rotation start determinationregion. Then, a point of time when the difference image integrated valueof the rotation start determination region exceeds a second threshold isdetermined as the rotation start time. Accordingly, a time at which achange in a specific region of the image becomes larger than a certaindegree from the initial state (stopped state) may be determined as therotation start time. That is, the rotation start time may be determinedby capturing a change caused in the image due to the rotation of thesubstrate holding unit, whereby it is possible to determine the rotationstart time with higher accuracy by using the easier algorithm.

In the present invention, a position of the rotation start determinationregion may be determined to a position at which the difference imageintegrated value is the maximum in the first image among the pluralityof first images photographed for every predetermined period from astopped state of the substrate holding unit to after a rotation startthereof, the first image being photographed before the first image forwhich the difference image integrated value is the maximum for the wholefirst images, and the first image being immediately before the firstimage in which a change of the difference image integrated value fromthe previous first image exceeds a predetermined third threshold.

Accordingly, first, it is possible to focus on the first image at apoint of time when the difference image integrated value is increasingbut has not become the maximum yet and is not very large, that is, in astate where the image has started to change due to the rotation start ofthe substrate holding unit. Then, within such first image, it ispossible to set a region having the maximum difference image integratedvalue, that is, a region in which the image changes the largest by therotation start, as the rotation start determination region. As a result,it is possible to detect the rotation start of the substrate holdingunit with high sensitivity or with higher accuracy.

In the present invention, the second threshold may be determined basedon an average value and a standard deviation of the difference imageintegrated value of the rotation start determination region of the firstimage during a stop of the substrate holding unit.

Accordingly, by focusing on the rotation start determination region asthe region in which the image changes the largest by the rotation of thesubstrate holding unit as described above, it is possible to determinethat the rotation is started from a change in the difference imageintegrated value exceeding a predetermine amount (second threshold) inthe rotation start determination region. Then, it is possible toappropriately determine the second threshold based on the statisticaldata of the difference image integrated value in the rotation startdetermination region of the first image during a stop of the substrateholding unit.

For example, by setting the second threshold as an averagevalue+3*standard deviation of the difference image integrated valueduring a stop of the substrate holding unit, it is possible to suppressinconvenience of being erroneously determined that the rotation of thesubstrate holding unit is started due to a statistical variation of thedifference image integrated value although the substrate holding unit isduring a stop.

In the present invention, the second threshold may be further determinedbased on a maximum value (MaxV) of the difference image integrated valueof the rotation start determination region of the first image during astop of the substrate holding unit and a minimum value (MinV) of thedifference image integrated value of the rotation start determinationregion of the first image at the rotation start time.

Here, in a case where there are multiple sets of the plurality of firstimages of the substrate and the substrate holding unit before and afterthe rotation start, in whole data of the multiple sets, it is possiblethat a minimum value (MinV) of the difference image integrated value ofthe rotation start determination region of the first image at therotation start time becomes smaller than the average value+3*standarddeviation of the difference image integrated value during the stop. Itis considered that such situation is caused by an abnormally largevariation in the difference image integrated value of the rotation startdetermination region of the first image during the stop or at therotation start time.

According to the present invention, in such case, it is possible tospecify the second threshold not by the average value+3*standarddeviation of the difference image integrated value and the like but byMaxV+(MinV−MaxV)*α(0<α<1), for example. Then, it is possible to set thesecond threshold to a numerical value equal to or greater than thedifference image integrated value during the stop and equal to orsmaller than the difference image integrated value at the rotation starttime, whereby it is possible to more certainly determine the rotationstart of the substrate and the substrate holding unit.

The present invention may be a substrate processing system including: asubstrate holding unit configured to rotate a substrate being held in asubstantially horizontal attitude; a processing control unit configuredto add predetermined processing to the substrate in a state where thesubstrate holding unit is rotated; and an abnormality inspection unitconfigured to inspect abnormality of a holding state of the substrate bythe substrate holding unit, the abnormality inspection unit including:an imaging unit configured to acquire a first image by photographing thesubstrate being held by the substrate holding unit from a horizontaldirection; a cut out unit configured to cut out, from the first image, asecond image corresponding to an inspection region positioned above thesubstrate being properly held by the substrate holding unit; and adetermination unit configured to obtain a feature quantity indicatingthe holding state of the substrate by the substrate holding unit and toperform abnormality determination of the holding state based on thefeature quantity on the second image, the substrate processing systemfurther including: an inspection region determination unit configured todetermine the inspection region for abnormality inspection of theholding state of the substrate, wherein the inspection regiondetermination unit includes: an upper end surface confirmation unitconfigured to confirm an upper end surface of the substrate beingnormally held by the substrate holding unit in the first image; avertical position determination unit configured to determine a positionof the inspection region in a vertical direction based on a position ofthe upper end surface of the substrate in the first image having beenconfirmed by the upper end surface confirmation unit; and a horizontalposition determination unit configured to, for a candidate of theinspection region for which the position in the vertical direction hasbeen determined, obtain density at a rotation start time of thesubstrate holding unit, obtain a difference image integrated value beingan integrated value of a difference absolute value with density of thesame region in an initial state of the substrate holding unit, anddetermine a horizontal position of the inspection region based on thedifference image integrated value having been obtained.

The present invention may be the above described substrate processingsystem, wherein the horizontal position determination unit positions thehorizontal position of the inspection region to a position at which thedifference image integrated value is the minimum.

The present invention may be the above described substrate processingsystem, wherein the upper end surface confirmation unit confirms theposition of the upper end surface of the substrate to a position atwhich a difference value of density between a pixel at a predeterminedhorizontal position of the first image and an adjacent pixel related tothe vertical direction is equal to or greater than a predeterminedmultiple of a standard deviation of density in each pixel related to thevertical direction.

The present invention may be the above described substrate processingsystem, wherein the feature quantity is determined based on thedifference image integrated value, and a threshold of the featurequantity used for the abnormality determination of the holding state ofthe substrate is determined based on an average value and a standarddeviation of the difference image integrated value in the inspectionregion of the first image during rotation of the substrate holding unit.

The present invention may be the above described substrate processingsystem, wherein the first image at the rotation start time of thesubstrate holding unit is an image in which the substrate being held bythe substrate holding unit is photographed from the horizontal directionby the imaging unit at a point of time when the difference imageintegrated value within a predetermined rotation start determinationregion exceeds a predetermined second threshold.

The present invention may be the above described substrate processingsystem, wherein a position of the rotation start determination region isdetermined to a position at which the difference image integrated valueis the maximum in the first image among the plurality of first imagesphotographed for every predetermined period from a stopped state of thesubstrate holding unit to after a rotation start thereof, the firstimage being photographed before the first image for which the differenceimage integrated value is the maximum for the whole first images, andthe first image being immediately before the first image in which achange of the difference image integrated value from the previous firstimage exceeds a predetermined third threshold.

The present invention may be the above described substrate processingsystem, wherein the second threshold is determined based on an averagevalue and a standard deviation of the difference image integrated valueof the rotation start determination region of the first image during astop of the substrate holding unit.

The present invention may be the above described substrate processingsystem, wherein the second threshold is further determined based on amaximum value of the difference image integrated value of the rotationstart determination region of the first image during a stop of thesubstrate holding unit and a minimum value of the difference imageintegrated value of the rotation start determination region of the firstimage at the rotation start time.

Note that the above-described Solution to Problem may be combined asappropriate when used.

According to the present invention, it is possible to decrease theworkload by automatically determining the inspection region particularlyto be focused on within the images, in a case where the abnormality ofthe holding state of the substrate is inspected by detecting the densitychange between the images before and after the rotation start of thesubstrate and the substrate holding member.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram illustrating a system configuration of a substrateprocessing system according to an example of the present invention;

FIG. 2 is a flowchart illustrating an operation of the substrateprocessing system according to the example of the present invention;

FIG. 3 is a flowchart illustrating a rotation start determination regiondetermination routine according to the example of the present invention;

FIG. 4 is a graph for describing a concept of MaxSum(n) according to theexample of the present invention;

FIG. 5 is a graph illustrating MaxSum(n) according to the example of thepresent invention in which a frame number is indicated on a horizontalaxis and V(n) of each frame is indicated on a vertical axis;

FIG. 6 is a graph for describing a provisional rotation startdetermination region according to the example of the present invention;

FIG. 7 is a flowchart illustrating a rotation start determinationthreshold determination routine according to the example of the presentinvention;

FIG. 8 is a table illustrating an average density variation value of therotation start determination region of three sets of pictures of a spinunit from a stopped state to a rotation start according to the exampleof the present invention;

FIG. 9 is a flowchart illustrating a rotation start positiondetermination routine according to the example of the present invention;

FIG. 10 is a flowchart illustrating a chuck abnormality determinationregion determination routine according to the example of the presentinvention;

FIG. 11 is a graph for describing algorithm for detecting an upper endsurface of a substrate according to the example of the presentinvention;

FIGS. 12A and 12B are second graphs for describing the algorithm fordetecting the upper end surface of the substrate according to theexample of the present invention;

FIG. 13 is a graph illustrating a width and a height of a chuckabnormality determination region and a gap amount from an upper endsurface of a wafer according to the example of the present invention;

FIGS. 14A and 14B are graphs for describing algorithm for determiningthe chuck abnormality determination region according to the example ofthe present invention;

FIG. 15 is a flowchart illustrating a chuck abnormality determinationthreshold determination routine according to the example of the presentinvention;

FIG. 16 is a view illustrating a basic configuration of a conventionalsubstrate holding unit; and

FIG. 17 is a view for describing the rotation start determination regionand the chuck abnormality determination region.

DETAILED DESCRIPTION First Example

Hereinafter, an example of the present invention is described withreference to the drawings. The example described below is one aspect ofthe present invention and is not intended to limit the technical scopeof the present invention.

In FIG. 1, a system configuration of a substrate processing system 10according to this example is illustrated. This system includes a spinunit 1 including a substrate holding member, a camera 2, an imageprocessing unit 3, an system main body control unit 4, and a displayunit 5.

In this system, in a state where a substrate W is rotated at apredetermined rotation speed by rotation of the spin unit 1 as asubstrate holding unit, processing of the substrate W is performed bysupplying a process liquid to the substrate W from a process liquiddischarge unit (not illustrated). The processing of the substrate W heremay include cleaning, surface treatment, and the like of the substrateW, for example. The process liquid supplied to a vicinity of a rotationcenter of the substrate W is spread toward an outer periphery side by acentrifugal force accompanying rotation of the substrate W, and finally,the process liquid is spun off from a peripheral edge portion of thesubstrate W to a side.

The camera 2 as an imaging unit acquires an image of the substrate W byimaging the spin unit 1 and the substrate W, which is held by the spinunit 1, from a horizontal direction. Hereinafter, the image photographedby the camera 2 may be referred to as a “horizontal image”. Thehorizontal image is equivalent to a first image according to the presentinvention. The horizontal image that has been acquired by the camera 2is transmitted to the image processing unit 3. The image processing unit3 performs predetermined image processing on the horizontal image andacquires information required for determining a holding state of thesubstrate W.

The system main body control unit 4 of the substrate processing system10 is provided with a CPU 4 a that controls an operation of each unit byexecuting a predetermined processing program, performs determination ofthe holding state of the substrate W, and performs the processing of thesubstrate W. The system main body control unit 4 is also provided with amemory 4 b for storing and saving the processing program executed by theCPU 4 a, data generated during processing, and the like. The system mainbody control unit 4 is connected to the display unit 5 for informing auser of a progress state of the processing, occurrence of abnormality,and the like as necessary. In this example, the system main body controlunit 4 is equivalent to a processing control unit. Furthermore, anabnormality inspection unit is constituted of the image processing unit3 and the system main body control unit 4.

FIG. 2 is a flowchart illustrating an operation of the substrateprocessing system 10. At least a part of this operation is achieved as aresult of execution of a predetermined processing program by the CPU 4a. First, in processing in step S11, the substrate W is set to the spinunit 1. Here, in a case where the substrate W is normally set to thespin unit 1, the substrate W is mechanistically held in a horizontalattitude. However, it is possible that the substrate W is set to thespin unit 1 abnormally due to reasons such as the substrate W is set ina state of running on any of the substrate holding members, thesubstrate holding members are not capable of horizontally holding thesubstrate W because a shape of the substrate holding members of the spinunit 1 has gradually been changed due to corrosion by a chemical liquidor the substrate W is held in an eccentric state, for example.

When the spin unit 1 and the substrate W are rotated in this state,there is a fear that the substrate W may drop off from the substrateholding members and may be damaged or that the substrate W may collideinto another member inside the system and may damage the system. Evenwhen the substrate W does not drop off, due to the substrate W rotatingin a tilted or eccentric state, there is a fear that abnormal vibration,which may be a cause of failure, may occur in the system. To preventsuch problem in advance, in this example, it is checked that thesubstrate W is normally rotated by the spin unit 1. Then, by using thehorizontal image photographed by the camera 2, the holding state of thesubstrate Win the spin unit 1, that is, whether or not the substrate Wis appropriately held by the substrate holding members of the spin unit1, is determined.

Specifically, while rotating the spin unit 1 at a low speed as describedin step S12, the substrate W is consecutively photographed at a fixedframe rate by the camera 2 (step S13). In so doing, it is possible toacquire about 15 horizontal images during one rotation by setting theframe rate to 30 frames per second (fps) and by accelerating the spinunit 1 at 500 rpm/s from a stopped state, for example.

Next, in step S14, an image of a rotation start determination region iscut out from the first horizontal image, and this image is stored in thememory 4 b as a rotation determination reference image. Then, an imageof the rotation start determination region is cutout from the secondhorizontal image, and for every pixel constituting this image, anabsolute value of a difference in density between a pixel and a pixel inthe rotation determination reference image corresponding to the pixel isobtained, and an integrated value thereof is calculated. Furthermore, bydividing the integrated value by an area of the rotation startdetermination region, an average value of the density difference iscalculated as a rotation determination value.

By the rotation determination value obtained this way becoming equal toor greater than a fixed reference value, it is possible to determinethat the spin unit 1 has shifted from a stopped state to a rotatingstate. Furthermore, in this example, in a case where it is determinedthat the rotation determination value is equal to or greater than thereference value in step S15, it is determined that a rotation start iscompleted, and the process moves into an inspection step (step S16). Onthe other hand, in a case where the rotation determination value issmaller than the reference value, it is determined as a rotation stop.The process returns to the processing in S14 and continues with rotationdetermination of the third horizontal image and after.

In the next step S16, while continuing rotation of then spin unit 1, thesubstrate W is consecutively imaged at a fixed frame rate by the camera2. Here, the frame rate is set to 30 fps, and 15 horizontal images areconsecutively acquired while the substrate W makes one turn. Every timethe horizontal image is acquired, an inspection region image is cut outfrom the horizontal image, and an average density value of theinspection region image is obtained. Furthermore, in step S17, astandard deviation of a density value of 15 inspection region images isobtained as a feature quantity indicating the holding state of thesubstrate W in the spin unit 1. It utilizes that the standard deviationof the density value of the inspection region images is greatlydifferent depending on whether or not the substrate W is appropriatelyheld. Note that the inspection region image that is cut out here isequivalent to a second image according to the present invention.

Then, in step S18, it is determined whether or not the standarddeviation obtained in step S17 is within an accepted range. In a casewhere it is determined to be within the accepted range in step S18, theprocess moves into an original substrate processing such as a cleaningstep (step S19). On the other hand, in a case where it is determinedthat the standard deviation exceeds the accepted range in step S18, therotation of the spin unit 1 is immediately stopped, and it is displayedon the display unit 5 that there is abnormality in holding of thesubstrate W to inform the user thereof (step S20). Note that the CPU 4 athat executes the processing in step S16 as described above isequivalent to a cut out unit according to the present invention.Furthermore, the CPU 4 a that executes the processing in step S18 isequivalent to a determination unit according to the present invention.

Next, there is described a method for automatically determining arotation start determination region and a rotation start determinationthreshold, which are used for determining the rotation start illustratedin FIG. 2, as well as a chuck abnormality determination region as theinspection region and a chuck abnormality determination threshold, whichare used for determining the holding state of the substrate W. Note thatin this example, it is assumed that automatic determination of therotation start determination region, the rotation start determinationthreshold, the chuck abnormality determination region, and the chuckabnormality determination threshold is executed when a condition of thesystem is changed such as when the system is introduced and when aposition of the camera 2 is changed, for example.

In FIG. 3, a flowchart of a rotation start determination regiondetermination routine according to this example is illustrated. Thisroutine is also a program executed by the CPU 4 a of the system mainbody control unit 4 and is stored in the memory 4 b.

When this routine is executed, first, in step S101, a picture of aprocess in which the spin unit 1 in a still state starts rotation isphotographed by the camera 2. A condition in so doing may be the same asthe photographing condition described in FIG. 2 in which the frame rateis set to 30 fps and the spin unit 1 is accelerated at 500 rpm/s fromthe stopped state, whereby about 15 horizontal images are acquiredduring one rotation.

Then, there is generated a difference absolute value image Sub(n) thatis an image illustrating an absolute value of a density difference ofeach pixel between a frame image Img(0) in an initial state, and an n-thframe image Img(n) among the plurality of frame images constituting theacquired picture. When processing in step S101 is completed, the routineproceeds to step S102.

In step S102, there is obtained Sum(n) that is a sum total of density ofeach pixel in the difference absolute value image Sub(n) that has beengenerated in step S101. Here, a relationship between the frame imageImg(0) in the initial state, the n-th frame image Img(n), the differenceabsolute value image Sub(n), and the sum total Sum(n) of the density ofeach of the pixels is as the following formula (1).

Sum(n)=Σ|Img(n)−Img(0)|=ΣSub(n)   (1)

When processing in step S102 is completed, the routine proceeds to stepS103.

In step S103, there is obtained MaxSum(n) that is the maximum value ofSum(1) to Sum(n) that has been obtained in step S102. In FIG. 4, a graphfor describing a concept of MaxSum(n) is illustrated. In FIG. 4, a framenumber of each of the frame images is indicated on a horizontal axis.The density difference integrated value Sum(n) of each of the frameimages is indicated on a vertical axis. As it is evident from FIG. 4, inthis example, Sum(n) of a frame 12 is the maximum, whereby Sum(n) of theframe 12 is the MaxSum(n). When processing in step S103 is completed,the routine proceeds to step S104.

In step S104, by further performing arithmetic of a formula (2) belowfor each MaxSum(n), an increment V(n) of the MaxSum(n) is obtained, andfurthermore, a frame number fmax having the maximum V(n) is obtained.

V(n)=MaxSum(n)−MaxSum(n−1)   (2)

In FIG. 5, related to the example of the MaxSum(n) illustrated in FIG.4, a graph is illustrated in which the frame number is indicated ahorizontal axis and V(n) of each frame is indicated on a vertical axis.In the example in FIG. 5, it is evident that fmax is 12. When processingin step S104 is completed, the routine proceeds to step S105.

Instep S105, for the frame image having a smaller frame number thanfmax, which has been obtained instep S104, V(k) is obtained such asV(fmax), V(fmax−1), V(fmax−2), and so on, and k is obtained such thatV(k) is equal to or smaller than a predetermined value. Then, k at thattime is referred to as a provisional rotation start position fstr. Inthis example, the predetermined value is set to 700 (×1000), and fstr isset to 11. In this example, to enable detection of the rotation start atan earliest possible stage after the rotation start, there is obtainedfstr that is the frame number in a state where the increment V(n) of theMaxSum(n) is not very large after the rotation start. As thepredetermined value, it is preferred that a value that suits a purposethereof be set in advance. When processing in step S105 is completed,the routine proceeds to step S106. Note that here, the predeterminedvalue 700 (×1000) is equivalent to a third threshold according to thepresent invention.

In step S106, by using a difference absolute value image Sub(fstr) atthe provisional rotation start position fstr (=11), a provisionalrotation start determination region is determined. More specifically, bycalling an image of Sub(11), as illustrated in FIG. 6, within arectangular region having a width w and a height h, a point that is theclosest to an origin within the region is defined as a reference point(x0, y0). Then, by changing this reference point (x0, y0), the wholeimage of the Sub(11) is scanned with the rectangular region to obtainthe reference point (x0, y0) at which a pixel density sum total of therectangular region is the maximum. Note that at that time, it ispreferred that the pixel density sum total/area of the rectangularregion (=average density variation value CutSum(x0, y0)) be derived foreach of the reference points (x0, y0). Then, the rectangular regionhaving the reference point (x0, y0) that is a point at which the pixeldensity sum total of the rectangular region is the maximum is set as aprovisional rotation start determination region Area(11). Whenprocessing in step S106 is completed, the routine proceeds to step S107.Note that the average density variation value is a value obtained bydividing the pixel density sum total by the area of the rectangularregion as described above; however, since the area of the rectangularregion is a fixed value, it is handled here in as a physical quantityactually having meaning equivalent to the pixel density sum total of therectangular region or an integrated value of pixel density of therectangle region.

In step S107, a determination step of a provisional rotation startdetermination region Area(k) described above is repeated M times (M=3 inthis example). A logical sum of all of the provisional rotation startdetermination regions Area(k), which have been obtained in each of thedetermination steps, is obtained and is set as a rotation startdetermination region Area. When processing in step S107 is completed,this routine is temporarily ended. In this routine, the rotation startdetermination region Area has been automatically determined.

Next, automatic calculation of the rotation start determinationthreshold is performed. In FIG. 7, a flowchart of a rotation startdetermination threshold determination routine according to this exampleis illustrated. This routine is also a program executed by the CPU 4 aof the system main body control unit 4 and is stored in the memory 4 b.As described in step S107 of the rotation start determination regiondetermination routine, in this example, the processing in steps S101 toS106 is repeated M times, and it is assumed that the picture of the spinunit 1 that starts rotation from the stopped state is photographed bythe camera 2 M times (M=3 in this example).

Then, when this routine is executed, first, instep S201, from among theM sets of pictures (M=3 in this example) of the spin unit 1 that startsthe rotation from the stopped state, the rotation start determinationregion Area is cut out from images of several frames before and afterthe rotation start of the spin unit 1, and an average density variationvalue CutSum(k) is obtained. A result thereof is exemplified in a tablein FIG. 8. In FIG. 8, the frame image at the provisional rotation startposition fstr has an offset of zero, the frame image before fstr has anoff set of a negative number, and the frame image after fstr has anoffset of a positive number.

Here, for the frame image having the offset from the provisionalrotation start position fstr of −12 to −2, the average density variationvalue CutSum(k) is clearly a small value, whereby it is considered thatthe spin unit 1 is definitely at a stop. For the frame image having theoffset from the provisional rotation start position fstr of −2 to −1,there is data indicating that the average density variation valueCutSum(k) is increasing, whereby it is a gray area whether or not thespin unit 1 is at a stop or is rotating. Furthermore, for the frameimage having the offset from the provisional rotation start positionfstr of 0 to 4, the average density variation value CutSum(k) is clearlya large value or is increasing, whereby it is considered that the spinunit 1 is definitely rotating. When processing in step S201 iscompleted, the routine proceeds to step S202.

In step S202, for CutSum(k) of the region having the offset of −12 to −2and is definitely at a stop, an average value Ave, a standard deviationStdev, and a maximum value MaxV are obtained. Furthermore, a minimumvalue MinV of CutSum(fstr) of three measurements illustrated in FIG. 8is obtained. When processing in step S202 is completed, the routineproceeds to step S203.

Instep S203, the maximum value MaxV of CutSum(k) of the region, which isdefinitely at a stop, obtained in step S202 is compared with the minimumvalue MinV of CutSum(fstr) in magnitude. In a case where it is MinVMaxV, it is not possible to set a threshold, whereby the routineproceeds to step S204. Then, an error display is performed in step S204,and this routine is temporarily ended. Here, a density change, straylight, reflected glare of an unnecessary image, large noise, and thelike are considered as a factor causing such error. On the other hand,in step S203, in a case where it is determined as MinV>MaxV, the routineproceeds to step S205.

In step S205, it is determined whether or not a formula (3) describedbelow is satisfied.

MaxV<Ave+3*Stdev≦MinV   (3)

Then, in a case where it is determined that the formula (3) is satisfiedin step S205, the routine proceeds to step S206. On the other hand, in acase where it is determined that the formula (3) is not satisfied instep S205, the routine proceeds to step S207.

In step S206, a recommended threshold Slice is set to Ave+3*Stdev.Accordingly, it is possible to obtain the recommended threshold Slicethat is larger than a substantially maximum value of variation ofCutSum(k) in a case where the spin unit 1 is at a stop. When processingin step S206 is completed, the routine proceeds to step S208.

In step S207, the formula (4) described below is satisfied.

MinV<Ave+3*Stdev   (4)

In this case, the recommended threshold Slice is set toMaxV+(MinV−MaxV)*α(0<α<1). Accordingly, it is possible to obtain therecommended threshold Slice existing between MaxV and MinV. Whenprocessing in step S207 is completed, the routine proceeds to step S208.

In step S208, it is determined whether or not the recommended thresholdSlice that has been set in step S206 or step S207 is equal to or smallerthan one. Here, in a case where it is determined that the recommendedthreshold Slice is equal to or smaller than one, the routine proceeds tostep S209, and the recommended threshold Slice is compulsorily set toone. When processing in step S209 is completed, this routine istemporarily ended. In a case where it is determined that the recommendedthreshold Slice is larger than one in step S208, this routine istemporarily ended as it is.

As above, by executing the rotation start determination thresholddetermination routine, it is possible to automatically determine therecommended threshold Slice, which is correspond to a second thresholdaccording to the present invention.

Next, in this example, further improving accuracy of the frame number atthe time of the rotation start is reconsidered by using FIG. 8. Theprovisional rotation start position fstr obtained in step S105 has beenobtained based on a difference absolute value image of the whole frameimage. On the other hand, in FIG. 8, the average density variation valueCutSum(k) has been obtained for the rotation start determination regionArea in which it is possible to more accurately evaluate the time of therotation start, whereby a rotation start position fstr2 having higheraccuracy is obtained by using FIG. 8.

In FIG. 9, a flowchart of a rotation start position determinationroutine according to this example is illustrated. This routine is also aprogram executed by the CPU 4 a of the system main body control unit 4and is stored in the memory 4 b.

When this routine is executed, first, in step S301, it is determinedwhether or not both of the following formulas (5) and (6) are satisfiedfor the recommended threshold Slice that has been determined in therotation start determination threshold determination routine.

Slice≦CutSum(fstr−1)   (5)

Slice>CutSum(fstr−2)   (6)

Then, in a case where it is determined that both of the formulas (5) and(6) are satisfied, the routine proceeds to step S302. On the other hand,in a case where it is determined that at least one of the formulas (5)and (6) are not satisfied, the routine proceeds to step S303.

In step S302, it is determined that the rotation start positionfstr2=fstr−1. When processing in S302 is completed, this routine istemporarily ended.

In step S303, it is determined whether or not both of the followingformulas (7) and (8) are satisfied for the recommended threshold Slicethat has been determined in the rotation start determination thresholddetermination routine.

Slice≦CutSum(fstr−1)   (7)

Slice≦CutSum(fstr−2)   (8)

Then, in a case where it is determined that both of the formulas (7) and(8) are satisfied, the routine proceeds to step S304. On the other hand,in a case where it is determined that at least one of the formulas (7)and (8) are not satisfied, the routine proceeds to step S305.

In step S304, it is determined that the rotation start positionfstr2=fstr−2. When processing in step S304 is completed, this routine istemporarily ended. In step S305, it is determined that the rotationstart position fstr2=fstr. When processing in step S304 is completed,this routine is temporarily ended.

As above, it is possible to determine the rotation start position fstr2having the higher accuracy.

Next, automatic determination of the chuck abnormality determinationregion is described. In FIG. 10, a flowchart of a chuck abnormalitydetermination region determination routine is illustrated. This routineis also a program executed by the CPU 4 a of the system main bodycontrol unit 4 and is stored in the memory 4 b. This routine is aroutine that performs (1) detection of an upper end surface of a waferfor a plurality of places in one frame image, (2) determination of aposition of the upper end surface of the wafer, and (3) determination ofthe chuck abnormality determination region. That is, in this routine,several search start points (X, 0) for searching a wafer edge areprovided, and a Y coordinate of the upper end surface of the wafer ateach of the points with a different X coordinate is detected. Forexample, in the frame image, each of the X coordinates of the searchstart points may be set at an interval of 20 pixels in a range of animage width*(0.2 to 0.8).

When this routine is executed, first, in step S401, in an image of awafer that is at a stop as illustrated in FIG. 11, to obtain the upperend surface of the wafer edge, density of each pixel is read in an Yaxial direction from each of the search start points (X(m), 0), and a3-nearest neighbor average is obtained. When processing in step S401 iscompleted, the routine proceeds to step S402.

In step S402, a difference value between the 3-nearest neighbor averageof each of the pixels and a 3-nearest neighbor average of an adjacentpixel as well as a standard deviation of the 3-nearest neighbor averageof each of the pixels are obtained. When processing in step S402 iscompleted, the routine proceeds to step S403.

In step S403, a first Y coordinate value at which the above-describedstandard deviation*predetermined gain (2.5 in this example) differencevalue is satisfied becomes a candidate of the upper end surface of thewafer. When processing in step S403 is completed, the routine proceedsto step S404. Here, the predetermined gain (2.5) is equivalent to apredetermined multiple according to the present invention.

In step S404, the Y coordinate of the above-described candidate of theupper end surface of the wafer is obtained for all X(m) of the frameimage. Then, an average and a standard deviation of the Y coordinatevalues of the candidate of the upper end surface of the wafer areobtained. When processing in step S404 is completed, the routineproceeds to step S405.

In step S405, from the average and the standard deviation of the Ycoordinate values of the candidate of the upper end surface of the waferthat have been obtained in step S404, an average±standard deviation iscalculated. Then, among the Y coordinates of the candidate of the upperend surface of the wafer obtained for all X(m) of the frame image, thereis calculated a frequency distribution of data within a range of theaverage±standard deviation. In FIG. 12A, the range of theaverage±standard deviation that has been obtained from the average andthe standard deviation of the Y coordinate values of the candidate ofthe upper end surface of the wafer is illustrated.

In FIG. 12B, among the Y coordinates of the candidate of the upper endsurface of the wafer obtained for all X(m) of the frame image, there isillustrated an exemplary frequency distribution of the data within therange of the average±standard deviation. Then, in the frequencydistribution of FIG. 12B, a Y coordinate value of a point where afrequency is the maximum becomes the Y coordinate of the upper endsurface of the wafer. Note that a singular point such as a point “1”illustrated in FIG. 11 is excluded by selecting only the Y coordinatewithin the range of the average±standard deviation as illustrated inFIG. 12A, whereby according to a method of this example, it is possibleto obtain the Y coordinate of the upper end surface of the wafer withhigher accuracy. When processing in step S405 is completed, the routineproceeds to step S406. Note that in the processing in steps S401 toS402, the 3-nearest neighbor average of each of the pixels is obtained,it has been focused on the difference value with the 3-nearest neighboraverage of the adjacent pixel; however, in the present invention, it isnot always necessary to obtain the 3-nearest neighbor average of each ofthe pixels. It is also possible to absorb variation of each of thepixels using a different method. In addition, it is not always necessaryto use one pixel as a unit of detection and comparison of density. Forexample, it is also possible to obtain an average of density of everytwo pixels and to obtain a difference value with an average of densityof adjacent two pixels. In this case, every two pixels are handled asone pixel.

In processing after step S406, the chuck abnormality determinationregion is determined. As an assumption of the processing in step S406,as illustrated in FIG. 13, a width and a height of the chuck abnormalitydetermination region and a gap amount thereof from the upper end surfaceof the wafer are determined in advance as parameters. Furthermore, bythe time when the processing in step S406 is executed, the Y coordinateof the upper end surface of the wafer has been determined, whereby Y0,which is a coordinate in a height direction of the chuck abnormalitydetermination region is determined based on the Y coordinate of theupper end surface of the wafer and the gap amount of the chuckabnormality determination region from the upper end surface of thewafer. When processing in step S406 is completed, the routine proceedsto step S407.

Instep S407, an X coordinate of a reference point for the chuckabnormality determination region is obtained. As for the X coordinate ofthe chuck abnormality determination region, in the same way ascalculation for obtaining the rotation start determination region, bychanging the X coordinate as illustrated in FIG. 14A, a position atwhich the pixel density sum total of the rectangular region in thedifference absolute value image is the minimum (hereinafter, alsoreferred to as a difference image integrated value) is set as areference X coordinate of the chuck abnormality determination region.Accordingly, it is possible to set a region in which there is no shadowof the substrate holding member and the like in the background as thechuck abnormality determination region, whereby it is possible to reducea probability of false report in a normal state and to improve detectionaccuracy of chuck abnormality. When processing in step S407 iscompleted, this routine is temporarily ended. Note that the differenceabsolute value image in step S407 may be an image illustrating anabsolute value of a density difference of each of the pixels between therectangular region in the frame image in the initial state and therectangular region in the frame image at the rotation start time, but isnot limited to this. It may also be an image illustrating the absolutevalue of the density difference of each of the pixels between therectangular region in the frame image in the initial state and therectangular region in the frame image at a predetermined time before orafter the rotation start. Furthermore, not limited to the above, it mayalso be an image illustrating the absolute value of the densitydifference of each of the pixels between the rectangular regions in twoframe images at two different points of time. In addition, it may alsobe an image illustrating the absolute value of the density difference ofeach of the pixels between the rectangular region at a coordinate (x,y0) and the rectangular region at a position at which the X coordinateis changed, for example, in the frame image at the same point of time.

Here, the CPU 4 a that executes the above-described chuck abnormalitydetermination region determination routine is equivalent to aninspection region determination unit according to the present invention.Furthermore, the processing in S401 to S405 is equivalent to an upperend surface confirming step according to the present invention, and theCPU 4 a that executes the processing in S401 to S405 is equivalent to anupper end surface confirmation unit according to the present invention.The processing in S406 is equivalent to a vertical positiondetermination step according to the present invention, and the CPU 4 athat executes the processing in S406 is equivalent to a verticalposition determination unit according to the present invention. Theprocessing in S407 is equivalent to a horizontal position determinationstep according to the present invention, and the CPU 4 a that executesthe processing in S407 is equivalent to a horizontal positiondetermination unit according to the present invention.

Next, automatic calculation of a threshold for determining the chuckabnormality is described. In FIG. 15, a flowchart of a chuck abnormalitydetermination threshold determination routine is illustrated. Thisroutine is also a program executed by the CPU 4 a of the system mainbody control unit 4 and is stored in the memory 4 b.

When this routine is executed, first, in step S501, by using thesubstrate W that is normally chucked to the spin unit 1, a chuckabnormality determination region Area 2 is cut out from an image ofseveral frames after the rotation start among all pictures in which thepicture of the spin unit 1 in a process of starting the rotation isphotographed by the camera 2 M times (M=3 in this example), and a pixeldensity sum total/Area (=average density variation value CutSum2 (k)) isobtained. Here, illustration of a table listing a detection value of theaverage density variation value CutSum2 (k) for each of the frame imagesis omitted. When processing in step S501 is completed, the routineproceeds to step S502.

In step S502, for the average density variation value CutSum2 (k) of thechuck abnormality determination region Area 2 in a period when it isdefinitely rotating, an average value Ave2, a standard deviation Stdev2,and a maximum value MaxV2 are obtained. When processing of step S502 iscompleted, the routine proceeds to step S503.

In step S503, a recommended threshold Slice2 is set to Ave2+3*Stdev 2.When processing in step S503 is completed, the routine proceeds to stepS504.

In step S504, it is determined whether or not the recommended thresholdSlice2 that has been set in step S503 is equal to or smaller than one.Here, in a case where it is determined that the recommended thresholdSlice2 is equal to or smaller than one, the routine proceeds to stepS505, and the recommended threshold Slice2 is compulsorily set to one.When processing in step S505 is completed, this routine is temporarilyended. In a case where it is determined that the recommended thresholdSlice2 is greater than one instep S504, this routine is temporarilyended as it is.

As above, by executing the chuck abnormality determination thresholddetermination routine, it is possible to automatically determine therecommended threshold Slice2.

REFERENCE SIGNS LIST

-   1 . . . spin unit-   2 . . . camera-   3 . . . image processing unit-   4 . . . system main body control unit-   5 . . . display unit

What is claimed is:
 1. An automatic determination method of aninspection region for abnormality inspection of a substrate holdingstate in a substrate processing system including: a substrate holdingunit configured to rotate a substrate being held in a substantiallyhorizontal attitude; a processing control unit configured to addpredetermined processing to the substrate in a state where the substrateholding unit is rotated; and an abnormality inspection unit configuredto inspect abnormality of a holding state of the substrate by thesubstrate holding unit, the abnormality inspection unit including: animaging unit configured to acquire a first image by photographing thesubstrate being held by the substrate holding unit from a horizontaldirection; a cut out unit configured to cut out, from the first image, asecond image corresponding to the inspection region positioned above thesubstrate being properly held by the substrate holding unit; and adetermination unit configured to obtain a feature quantity indicatingthe holding state of the substrate by the substrate holding unit and toperform abnormality determination of the holding state based on thefeature quantity on the second image, the automatic determination methodcomprising: upper end surface confirming in which an upper end surfaceof the substrate being normally held by the substrate holding unit isconfirmed in the first image; vertical position determining in which aposition of the inspection region in a vertical direction is determinedbased on a position of the upper end surface of the substrate in thefirst image having been confirmed in the upper end surface confirming;and horizontal position determining in which, for a candidate of theinspection region for which the position in the vertical direction hasbeen determined, density at a rotation start time of the substrateholding unit is obtained, a difference image integrated value being anintegrated value of a difference absolute value with density of the sameregion in an initial state of the substrate holding unit is obtained,and a horizontal position of the inspection region is determined basedon the difference image integrated value having been obtained.
 2. Theautomatic determination method of the inspection region for theabnormality inspection of the substrate holding state according to claim1, wherein in the horizontal position determining, the horizontalposition of the inspection region is a position at which the differenceimage integrated value is the minimum.
 3. The automatic determinationmethod of the inspection region for the abnormality inspection of thesubstrate holding state according to claim 1, wherein in the upper endsurface confirming, the position of the upper end surface of thesubstrate is confirmed to a position at which a difference value ofdensity between a pixel at a predetermined horizontal position of thefirst image and an adjacent pixel related to the vertical direction isequal to or greater than a predetermined multiple of a standarddeviation of density in each pixel related to the vertical direction. 4.The automatic determination method of the inspection region for theabnormality inspection of the substrate holding state according to claim1, wherein the feature quantity is determined based on the differenceimage integrated value, and a threshold of the feature quantity used forthe abnormality determination of the holding state of the substrate isdetermined based on an average value and a standard deviation of thedifference image integrated value in the inspection region of the firstimage during rotation of the substrate holding unit.
 5. The automaticdetermination method of the inspection region for the abnormalityinspection of the substrate holding state according to claim 1, whereinthe first image at the rotation start time of the substrate holding unitis an image in which the substrate being held by the substrate holdingunit is photographed from the horizontal direction by the imaging unitat a point of time when the difference image integrated value within apredetermined rotation start determination region exceeds apredetermined second threshold.
 6. The automatic determination method ofthe inspection region for the abnormality inspection of the substrateholding state according to claim 5, wherein a position of the rotationstart determination region is determined to a position at which thedifference image integrated value is the maximum in the first imageamong the plurality of first images photographed for every predeterminedperiod from a stopped state of the substrate holding unit to after arotation start thereof, the first image being photographed before thefirst image for which the difference image integrated value is themaximum for the whole first images, and the first image beingimmediately before the first image in which a change of the differenceimage integrated value from the previous first image exceeds apredetermined third threshold.
 7. The automatic determination method ofthe inspection region for the abnormality inspection of the substrateholding state according to claim 5, wherein the second threshold isdetermined based on an average value and a standard deviation of thedifference image integrated value of the rotation start determinationregion of the first image during a stop of the substrate holding unit.8. The automatic determination method of the inspection region for theabnormality inspection of the substrate holding state according to claim7, wherein the second threshold is further determined based on a maximumvalue of the difference image integrated value of the rotation startdetermination region of the first image during a stop of the substrateholding unit and a minimum value of the difference image integratedvalue of the rotation start determination region of the first image atthe rotation start time.
 9. A substrate processing system comprising: asubstrate holding unit configured to rotate a substrate being held in asubstantially horizontal attitude; a processing control unit configuredto add predetermined processing to the substrate in a state where thesubstrate holding unit is rotated; and an abnormality inspection unitconfigured to inspect abnormality of a holding state of the substrate bythe substrate holding unit, the abnormality inspection unit including:an imaging unit configured to acquire a first image by photographing thesubstrate being held by the substrate holding unit from a horizontaldirection; a cut out unit configured to cut out, from the first image, asecond image corresponding to an inspection region positioned above thesubstrate being properly held by the substrate holding unit; and adetermination unit configured to obtain a feature quantity indicatingthe holding state of the substrate by the substrate holding unit and toperform abnormality determination of the holding state based on thefeature quantity on the second image, the substrate processing systemfurther comprising: an inspection region determination unit configuredto determine the inspection region for abnormality inspection of theholding state of the substrate, wherein the inspection regiondetermination unit includes: an upper end surface confirmation unitconfigured to confirm an upper end surface of the substrate beingnormally held by the substrate holding unit in the first image; avertical position determination unit configured to determine a positionof the inspection region in a vertical direction based on a position ofthe upper end surface of the substrate in the first image having beenconfirmed by the upper end surface confirmation unit; and a horizontalposition determination unit configured to, for a candidate of theinspection region for which the position in the vertical direction hasbeen determined, obtain density at a rotation start time of thesubstrate holding unit, obtain a difference image integrated value beingan integrated value of a difference absolute value with density of thesame region in an initial state of the substrate holding unit, anddetermine a horizontal position of the inspection region based on thedifference image integrated value having been obtained.
 10. Thesubstrate processing system according to claim 9, wherein the horizontalposition determination unit positions the horizontal position of theinspection region to a position at which the difference image integratedvalue is the minimum.
 11. The substrate processing system according toclaim 9, wherein the upper end surface confirmation unit confirms theposition of the upper end surface of the substrate to a position atwhich a difference value of density between a pixel at a predeterminedhorizontal position of the first image and an adjacent pixel related tothe vertical direction is equal to or greater than a predeterminedmultiple of a standard deviation of density in each pixel related to thevertical direction.
 12. The substrate processing system according toclaim 9, wherein the feature quantity is determined based on thedifference image integrated value, and a threshold of the featurequantity used for the abnormality determination of the holding state ofthe substrate is determined based on an average value and a standarddeviation of the difference image integrated value in the inspectionregion of the first image during rotation of the substrate holding unit.13. The substrate processing system according to claim 9, wherein thefirst image at the rotation start time of the substrate holding unit isan image in which the substrate being held by the substrate holding unitis photographed from the horizontal direction by the imaging unit at apoint of time when the difference image integrated value within apredetermined rotation start determination region exceeds apredetermined second threshold.
 14. The substrate processing systemaccording to claim 13, wherein a position of the rotation startdetermination region is determined to a position at which the differenceimage integrated value is the maximum in the first image among theplurality of first images photographed for every predetermined periodfrom a stopped state of the substrate holding unit to after a rotationstart thereof, the first image being photographed before the first imagefor which the difference image integrated value is the maximum for thewhole first images, and the first image being immediately before thefirst image in which a change of the difference image integrated valuefrom the previous first image exceeds a predetermined third threshold.15. The substrate processing system according to claim 13, wherein thesecond threshold is determined based on an average value and a standarddeviation of the difference image integrated value of the rotation startdetermination region of the first image during a stop of the substrateholding unit.
 16. The substrate processing system according to claim 15,wherein the second threshold is further determined based on a maximumvalue of the difference image integrated value of the rotation startdetermination region of the first image during a stop of the substrateholding unit and a minimum value of the difference image integratedvalue of the rotation start determination region of the first image atthe rotation start time.